With the model, I was able to show that plants acquired nutrients in proportion to the fraction of all the root length they had in a given volume of soil. Plants had a lot more roots than they needed to take up nutrients...if there was no competition. Once more than one plant had roots in a given volume of soil, a race set in.

As a result, plants can have 1000 times more roots that is optimal for maximizing growth.

That all pertained to nutrients though.

I'm curious about how competition for water works.

For example, does competition for water favor plants with high root length density? Would this also lead to a race like nutrients.

For competitive purposes, is there any benefit to being able to sustain a low minimum water potential? Under what conditions, if any, does drought tolerance affect competitive outcomes?

I'm also curious about the interactions between nutrients and water. Does increasing transpiration rate help with nutrient competition? Do dry soils exacerbate nutrient limitation?

But first, I need to adjust the model to handle water.

That means making soil moisture dynamic, parameterizing water fluxes between pixels and into roots.

The hardest part of all of this is figuring out how to parameterize water uptake by a given root. There is no simple Michaelis-Menten equation here. Roots are a 1000 connected little straws

Still, I've been impressed by some of the developments in root modeling over the past few years.